#define _CRT_SECURE_NO_WARNINGS 1

#include<stdio.h>

int main()
{
	int a = 70;
	int b = 20 + 15 + 5;
	int count = 0;
	while (a != b)
	{
		a++;
		b += 3;
		count++;
	}
	printf("%d", count);

	return 0;
}